Evaporative non-mechanical heatsink refrigeration system



H. B. ELLIS Sept. 5, 1967 EVAPORATIVE NON-MECHANICAL HEAT-SINK REFRIGERATION SYSTEM 2 Sheets-Sheet 1 Filed April 5, '1965 FIG. --2

INVENTOR. HERBERT B ELLIS BY 5, 3M

ATTORNEYS H B. ELLIS Sept. 5, 1967 EVAPORATIVE NON-MECHANICAL HEAT-SINK REFRIGERATION SYSTEM 2 SheetsSheet 2 Filed April 5, 1965 IIIIIIIIIIIIIIIIJIIIIIII/I INVENTOR. HERBERT B. ELLIS BY MQM Cmaw ATTORNEYS United States Patent 3,339,374 EVAPORATIVE NON-MECHANICAL HEAT- SINK REFRIGERATION SYSTEM Herbert B. Ellis, Pasadena, Calif., assignor to Aeroiet- General Corporation, El Monte, Calif., a corporation of Ohio Filed Apr. 5, 1965, Ser. No. 447,605 Claims. (Cl. 62-113) ABSTRACT OF THE DISCLOSURE An evaporative, heat-sink system having a non-insulated metal container positioned wholly within the refrigerated enclosure and a pressure actuated valve in communication with said container for discharging evaporated refrigerant to the atmosphere with optional means for passing the evaporated refrigerant in heat-sink relationship with the refrigerant of the metal container prior to discharge to the atmosphere.

This application is a continuation-impart of my copending application Ser. No. 394,126, filed Sept. 3, 1964, now abandoned, entitled, Apparatus, and assigned to the same assignee as the present application.

This invention pertains to a novel refrigeration system generally, and specifically relates to a refrigeration system of the evaporative type.

Transport refrigeration forms an important part of the food distribution system. A satisfactory evaporative transport refrigeration system should have characteristics not yet fully achieved by the different systems now in operation. These desirable characteristics include: (1) applicability to both fresh and frozen food shipments; (2) no temperature below any critical temperature for the perishables being refrigerated; (3) a control system that effectively responds to the total refrigerated space condition and is not affected by rapid local changes and corresponding relatively numerous rapid actuation cycles; (4) a distribution of refrigeration in accordance with these space requirements without mechanically forced convection, and with relatively small temperature differences; (5) a minimum of the impairment of the effective loading volume; (6) a ready attachment to transport equipment structures so as to withstand both static and dynamic loadings.

Various types of heat-sink refrigeration systems are known. These systems of the prior art primarily utilizing liquid nitrogen or liquid carbon dioxide refrigerants, comprise a pressurized storage tank and a thermostatically controlled liquid discharge valve. When the temperature within the refrigerated space rises above the control temperature, the thermostat electrically or pneumatically causes the valve to open permitting a discharge of the liquid or gaseous refrigerant into the refrigerated space. When the temperature drops to the control temperature, the valve closes. In all these systems the liquid refrigerant storage tank can be placed either inside or outside the refrigerant space.

In another known evaporative system, the refrigerant container inside the refrigerated space is insulated to provide variable and controllable heat transfer to the liquid refrigerant. The extent to which the liquid refrigerant container is insulated determines the minimum amount of continuous refrigeration provided. The external surface 3,339,374 Patented Sept. 5, 1967.

causing increased evaporation rates and resulting increased refrigeration.

Accordingly, it is an object of the present invention to provide a novel evaporative refrigeration system. Another object of this invention is to provide a novel refrigeration system characterized by greater control and uniformity of temperature. Still another object of this invention is the provision of a novel method of evaporative non-mechanical, heat-sink refrigeration. These and other objects of this invention will be apparent from the detailed description which follows. v

The novel refrigeration system of my invention provides numerous advantages over evaporative refrigeration systems known in the prior art. In the system I have invented, a container of liquid refrigerant is positioned in the refrigerated space and is in direct heat transfer relationship with the atmosphere within the refrigerated space. The heat from the atmosphere of the refrigerated space is transferred to the refrigerant by convection and conduction. The temperature of the refrigerant is determined by the setting of a simple pressure regulative valve and the saturation temperature-pressure relationship characteristics of the refrigerant. By a proper setting of the valve, an adequate temperature control for either fresh or frozen food is achieved.

Physically, the refrigeration system I have invented comprises, in one preferred embodiment, a multiplicity of liquid refrigerant pipes positioned along the length of the ceiling of the refrigerated space. These pipes are interconnected so one fill position and one pressure regulated outlet are required. The pipes in this form and position are in the warmest part of the refrigerated spaceand can most effectively, by the use of free convection of the atmosphere in the refrigerated space, provide cooling where and when as required. As the pipes extend the entire length of the ceiling, any local warm regions are automatically controlled. As a local temperature difference increases by the refrigerated space temperature increasing, more cooling effect is locally applied where it is needed. The needs of different loads packed in different patterns is automatically handled. A thermostat and a network of refrigerant spray nozzles cannot provide the automatic adjustment inherent in the interconnected pipe, pressure regulated system.

The evaporative, non-mechanical, heat-sink refrigeration system of this invention includes an essentially fluid tight insulated enclosure having received therein a container attached to hold refrigerant under pressure. The container is positioned within the enclosure so that it is in direct heat transfer relationship with the atmosphere within the enclosure. In pressure-tight communication with the container is a pressure actuated valve means. This valve is equipped with an adjustment means whereby the valve may be set to open in response to any predetermined pressure created by the refrigerant within the container. The pressure actuated valve is the sole moving part in the system.

The refrigerant vapors, in passing through the pressure actuated valve means, are substantially chilled by the expansion of the vapors. Vapors may be discharged directly, either within or without the insulated enclosure. I have found, however, that certain additional advantages are achieved. by first passing the vapors from the valve in heat-transfer relationship with the refrigerant container before discharge, whether inside or outside the insulated enclosure. This provides realization of more refrigerating effect per quantity of refrigerant, as well as improvement of the uniformity of temperature to which the material being refrigerated is exposed.

These and other objects, aspects, features and advantages of the invention will be apparent to those skilled in the art from the following more detailed description taken in conjunction with the drawings, wherein:

FIG. 1 is a sectional view of one embodiment of the refrigeration system of this invention;

FIG. 2 is a cross-section of the device shown in FIG- URE 1 taken along line 22;

FIG. 3 is a cross-section of another embodiment of the refrigeration system of this invention; and

FIG. 4 is a sectional view of the embodiment of FIG- URE 1, incorporating the heat exchange feature, whereby the expanded vapors are passed in heat-transfer relationship with the refrigerant container, before discharge.

With particular reference to FIGURE 1, enclosure 1 has contained within it a non-insulated metal container 2 adapted to hold refrigerant. This container is also equipped with a filler line and valve 3 through which the necessary refrigerant is charged prior to use of the system. Leading from the container is a line 4 connecting to a pressure actuated valve 5. The line 4 maintains the valve 5 in pressure-tight communication with the container 2. The valve is equipped with adjustment means 6 which is calibrated to be set so that valve 5 can be made to open in response to any predetermined pressure within container 2. Leading from valve 5 is a means 7 for discharging the evaporated refrigerant at atmospheric pressure.

The adjustable, pressure actuated valve utilized in the refrigeration system of this invention is available on the commercial market, and is familiar to those skilled in the art. Accordingly, its structure need not be described in greater detail here.

As already indicated, FIGURE 2 is a cross-section of the device shown in FIGURE 1 taken along line 2-2. As can be seen the horizontal area of container 2 is approximately co-extensive with the area of the ceiling of the enclosure 1. As shown, enclosure 1 is preferably of multi-layer construction, having an inner and outer covering of solid sheet material having substantial structural integrity, and an intermediate insulation layer 8.

FIGURE 3 is a cross-section of another embodiment of the refrigerator system of this invention. In this embodiment the container for the refrigerant 9 consists of a bank of continuous interconnected pipes. Each of the pipes shown is connected to the adjacent pipe by a U- joint. The refrigerant is charged to the system through line 10. The pressure and hence the boiling point of the refrigerant, as well as the temperature in the container, are maintained at any desired level in accordance with the pressure selection made on pressure operated valve 11. The evaporated refrigerant is discharged to the atmosphere through line 12. In general the use of a plurality of interconnected pipes as the refrigerant container is preferred since it increases the contact area between the container and the atmosphere within the enclosure. This provides for even better heat transfer and resultant greater uniformity in the temperature throughout the enclosure.

A multiplicity of relatively small diameter full length interconnected pipes hung just below the ceiling of the refrigerated space also offers a minimum of interference with the use of the refrigerated space. The refrigerated floor space or wall space is not cut up, but remains fiat and full length. Loose packed fresh foods such as meat are often hung from rails along the ceiling. The normal space. There are no heavy massed concentration points tween either the rails and the pipes, or the hanging meat in the pipes. The installation of the multiple pipe refrigeration system is simple since the weight is distributed throughout the length and breadth of the refrigerated space. There are no heavy massed concentration points that require strengthening of the transport vehicle structure to withstand the accelerations and shock loading present during transport operations.

The amount of evaporative refrigerating effect obtained from an evaporative refrigerant is the amount of heat the refrigerant will absorb between its initial condition and the condition in which it leaves the refrigerated transport equipment. In thermodynamic terms, this is the difference in heat content or enthalpy of the refrigerant between the start and finished conditions of state, pressure, and temperature. Thermodynamic charts or tables provide the enthalpy or heat-content condition. In the start condition for the liquid refrigerant, the heat content varies with the pressure and temperature. In the evaporative system of this invention, the liquid refrigerant is stored at saturation conditions, which defines the temperature for each pressure. For an example, the effect of the storage pressure, commonly used for liquid nitrogen is that liquid nitrogen stored at 20 pounds per square inch contains 10 B.t.u. per-pound more heat than when stored at atmospheric pressure. Liquid carbon dioxide when stored at +40 F. contains 33 B.t.u. per pound more heat than when stored at 22 F.

The heat content of the vapor leaving the refrigeration equipment may also have different heat contents. If liquidnitrogen vapor leaves the refrigerated equipment directly at the refrigeration temperature of 10 F. and one atmosphere pressure, it contains 21 B.t.u. per pound less heat than vapor leaving the refrigeration equipment at F. Similarly, carbon dioxide vapors at 10 F. and one atmosphere contain 17 B.t.u. per pound less heat than that at +75 F. Consequently, the refrigerating effect depends upon the liquid refrigerant condition and the leaving evaporated refrigerant condition.

In the operation of the system of FIGURE 1, the setting of valve 5 determines the boiling temperature of the refrigerant within container 2. The lower the pressure at which valve 5 is set to open, the lower will be the temperature at which the refrigerant within container 2 boils. The lower the boiling temperature within container 2, the lower the temperature within enclosure 1. In Table I, below, the relationship between the pressure setting on valve 5 (column 1), the boiling temperature of the refrigerant within enclosure 2 (column 2), the temperature of the atmosphere within enclosure 1 (column 3), and the outside air temperature (column 4), in a typical system wherein the refrigerant is carbon dioxide is set forth.

It will be seen that by a proper setting of valve 5, the temperature within the enclosure 1 may be maintained at any desired temperature level within a wide range. The system provided by this invention therefore is possessed of great flexibility, and is accordingly adapted to the refrigeration of both fresh and frozen foods.

As shown in FIGURE 1, the evaporated refrigerant may be discharged through the wall of enclosure 2. In the embodiment depicted in FIGURE 1, valve 5 is located within enclosure 2. However, it is also envisioned that the valve may be located outside the enclosure. This may be accomplished simply by extending line 4 through the wall of enclosure 2. Alternatively, the evaporated refrigerant may be discharged within the enclosure, thus more fully utilizing the cooling capacity of the refrigerant.

As indicated above, I have found that certain additional advantages are achieved by passing the expanded vapors in heat-transfer relationship with the refrigerant container before discharging them.

necting to a pressure-actuated valve 25, having a pres sure level adjustment means 26, said valve being in pressure-tight communication with the container 22. From the valve 25 is provided a pipe means 29, covered with an insulating layer 30, for conducting the expanded vapors to a heat exchanger 31. The heat exchanger can be of any design, such as a simple tube of sufficient length passing through the container 22, with the cold expanded vapors flowing through the inside of the tube of the heat exchanger 31. The positioning of the tube 31 in the top portion of the container 22, where it is primarily exposed to the high pressure vapors in the container 22, is preferred, but it can be totally encompassed by liquid refrigerant. The heat exchanger 31 exhausts to the atmosphere through a discharge pipe means 27, although it could exhaust into the enclosure 21.

In operation of the apparatus of FIGURE 4, it is to be understood that evaporative refrigerants, such as carbon dioxide, have a characteristic of a significant drop in the temperature of their vapors upon undergoing an expansion. For example, in use of this refrigeration system for fresh food, maintenance of the refrigerant in the container tank 22 at +35 F. would be typical. The expansion of the carbon dioxide vapors from this pressure condition of 528 p.s.i.a. to atmospheric pressure through the pressure actuated value 25 would cause the temperature of the vapors to drop to 90 F. When these cold vapors are discharged directly to the atmosphere outside the enclosure 21, valuable refrigeration effect is lost. When these vapors are discharged directly into the enclosure 21, the fresh food is subject to the danger of be ing frozen in local regions exposed to the below freezing temperatures of the chilled vapors. To avoid the loss of refrigerating effect on one hand, and to improve the uniformity of the refrigerating temperature on the other hand, passing the chilled vapors through a heat exchanger 31 in the refrigerant container 22 results in realizing the full refrigerating effect, as well as warming the vapors up to the refrigeration container temperature before the vapors are discharged. To protect the material being refrigerated from the low temperature which will exist between the pressure actuated valve 25 and the heat exchanger 31, the pipe means 29 is covered with sufiicient insulation 30 to prevent undesirable local chilling.

The system of this invention can be built into a truck trailer or a railroad car as well as finding other applications which will be readily apparent to those skilled in the art.

The refrigeration method may be carried out in apparatus unlike that described above. For example, an ordinary manually operated valve may be used to maintain the refrigerant under a constant predetermined pressure. By equipping the refrigerant container with a pressure gage, the valve may be manipulated by hand at periodic intervals to keep the pressure at the desired level.

Thenovel evaporative refrigeration system and method of this invention is particularly adapted for use in underdeveloped countries. In contrast to mechanical refrigeration systems, it offers a simple system with one moving part. It is more reliable, easier to service, requires the stocking of a minimum of repair parts, and is capable of meeting a wider range of refrigeration demands than the mechanical system. With respect to other evaporative systems, the novel evaporative refrigeration system of this invention is superior in safely refrigerat- Having fully described the invention, it is intended that it be limited only by the lawful scope of the appended claims.

I claim:

1. In an evaporative, non-mechanical, heat-sink method of referigeration of an enclosure containing articles to be refrigerated, the steps comprising:

' providing a non-insulated metal container positioned wholly within said enclosure and holding a refrigerant under pressure therein with the surface of said metal container being in direct heat transfer relationship with the atmosphere within the enclosure, said refrigerant within the container comprising liquid partially filling said container and expanded vapor occupying the rest of the container;

evaporatively releasing said refrigerant from said metal container and discharging to atmospheric pressure; and

prior to discharge to atmospheric pressure passing said released vapors in heat-transfer relationship with the refrigerant in said metal container, whereby the vapor pressure over said liquid body of refrigerant within the container is maintained at a constant predetermined level.

2. An evaporative, non-mechanical, heat-sink refrigeration system comprising:

an essentially fluid-tight insulated enclosure;

a non-insulated metal container postioned wholly Within said enclosure and adapted to hold refrigerant under pressure received therein, the surface of said container being in direct heat-transfer relationship with the atmosphere within the enclosure;

a refrigerant within the container comprising liquid partially filling said container and expanded vapor occupying the rest of the container;

a pressure actuated valve in pressure-tight communication with said container, said valve having an adjustment means for setting the valve to open in response to a predetermined pressure within said container; and

means in heat-transfer relationship with the interior of said container for dis-charging evaporated refrigerant at normal atmospheric pressure.

3. An evaporative, non-mechanical, heat-sink refrigeration system comprising:

an essentially fluid-tight, insulated enclosure;

a non-insulated metal container positioned wholly within said enclosure and adapted to hold refrigerant under pressure received therein, the surface of said container being in direct heat-transfer relationship with the atmosphere within the enclosure;

a refrigerant within the container comprising liquid partially filling said container and expanded vapor occupying the rest of the container;

a pressure actuated valve in pressure-tight communication with said container;

means for discharging evaporated refrigerant at normal atmospheric pressure after it has passed through said valve; and

said discharge means being arranged in heat-transfer relationship with the interior of said container.

4. An evaporative, non-mechanical, heat-sink refrigeration system comprising:

an essentially fluid-tight, insulated enclosure;

a non-insulated metal container positioned wholly within said enclosure and adapted to hold refrigerant under pressure received therein, the surface of said container being in direct heat-transfer relationship with the atmosphere with the enclosure;

a refrigerant within the container comprising liquid partially filling said container and expanded vapor occupying the rest of the container;

a pressure actuated valve in pressure-tight communication with said container, said valve having an adjustment means for setting the valve to open in response to a predetermined pressure with said container;

means leading from said valve for discharging evaporated refrigerant at normal atmospheric pressure; and

said discharge means being arranged in heat-transfer relationship with the interior of said container.

5. An evaporative, non-mechanical, heat-sink refrigeration system comprising:

an essentially fluid-tight, insulated enclosure;

a non-insulated metal container positioned wholly within said enclosure and adapted to hold refrigerant under pressure received therein, the surface of said container being in direct heat-transfer relationship with the atmosphere within the enclosure, the container having a filler means for introducing liquid refrigerant into the interior thereof;

a refrigerant within the container comprising liquid partially filling said container and expanded vapor occupying the rest of the container;

a pressure actuated valve in pressure-tight communication with said container, said valve having an adjustment means for setting the valve to open in response to a predetermined pressure within said container;

means leading from said valve for discharging evaporated refrigerant at normal atmospheric pressure; and

said discharge means being arranged in heat-transfer relationship with the interior of said container.

References Cited UNITED STATES PATENTS 2,374,972 5/1945 Biehl 622l7 X 2,496,816 2/1950 Schlumbohm 62514 X 2,925,722 2/1960 Blackburn 62-514 X 3,092,977 6/1963 Skinner 62514 X MEYER PERLIN, Primary Examiner. 

1. IN AN EVAPORATE, NON-MECHANICAL, HEAT-SINK METHOD OF REFERIGERATION OF AN ENCLOSURE CONTAINING ARTICLES TO BE REFRIGERATED, THE STEPS COMPRISING: PROVIDING A NON-INSULATED METAL CONTAINER POSITIONED WHOLLY WITHIN SAID ENCLOSURE AND HOLDING A REFRIGERANT UNDER PRESSURE THEREIN WITH THE SURFACE OF SAID METAL CONTAINER BEING IN DIRECT HEAT TRANSFER RELATIONSHIP WITH THE ATMOSPHERE WITHIN THE ENCLOSURE, SAID REFRIGERANT WITHIN THE CONTAINER AND EXPANDED VAPOR OCCUPYING THE REST OF THE CONTAINER; EVAPORATIVELY RELEASING SAID REFRIGERANT FROM SAID METAL CONTAINER AND DISCHARGING TO ATMOSPHERIC PRESSURE; AND PRIOR TO DISCHARGE TO ATMOSPHERIC PRESSURE PASSING SAID RELEASED VAPORS IN HEAT-TRANSFER RELATIONSHIP WITH THE REFRIGERANT IN SAID METAL CONTAINER, WHEREBY THE VAPOR PRESSURE OVER SAID LIQUID BODY OF REFRIGERANT WITHIN THE CONTAINER IS MAINTAINED AT A CONSTANT PREDETERMINED LEVEL. 